eat more food, dont listen to the people who say you need to lose weight. you're overthinking this and the whole idea that the lighter you are the faster you'll move. thats onyl true if youre already carrying unnecesary weight (a lot of extra water weight, heavy clothing/shoes, having eaten a large meal just before you ran, etc.).
you solved the case for yourself when you said you die out earlier in the season off little food. even if you eat a large amount of food you still burn it off and the energy that you get from the food is more efficient than running on little food because you have more energy to use.
as a high mileage runner, and a college runner nonetheless, you need A LOT of energy to be able to not only compete at the highest level but also to be able to function properly. if your doing anywhere from 60 mpw and upwards of that you'd most likely need bare minimum 3000 calories but closer to 4000-5000 with more mileage.
just eat healthy and dont eat empty calories like a previous poster said. dont aganonize over your weight,
have a balanced diet and dont try starving yourself to lose weight. a classic example is the website someone posted a few weeks ago about a female college runner who she and her team went through the same thing your talking about; they though they'd do better if they weighed less.
i'm also an example of what happens when you dont eat; i thought that if i lost weight it would help my running (lighter=faster was the mindset). i was doing around 50-60 mpw and not eating nearly as much as i should have to the point where after a mile of say an 8 mile run I'd feel exhausted and couldnt hold my normal training pace. not only was i extremely exhausted and couldnt run at my normal pace anymore but i started getting sick, injured and was just doing poorly. i became anemic and it destroyed my entire year i was so malnourished. in fact, it got to the point that in order to function semi-normally my body starting taking its nutrients from muscle and bone (it literally ate itself). i havent been able to run more than 8 mpw in months before my shins start hurting so much to the point that i cant walk. then i'm layed up again in the pool for another 3 weeks. bone takes a VERY long time to heal so dont try what i did, keep eating.